1. Field of the Invention
The present invention relates to an electronic arrangement for the determination of reactive power, consisting of two transducers which are provided for connection to an electrical power supply, delivering at their outputs measuring voltages proportional to the power supply current and the power supply voltage; a multiplier element with two inputs for the processing of the two measuring voltages and delivering at its output a signal proportional to the reactive power, as well as including at least one phase shifting element connected to the input of the multiplier element for the generation of an additional phase displacement of 90.degree. between the measuring voltages.
2. Discussion of the Prior Art
Arrangements of that type are commercially obtainable as reactive power measuring apparatuses for alternating current voltage. Hereby, one input of the multiplier element has an RC element connected ahead thereof as a phase shifting element for the generation of an additional phase displacement of 90.degree.. This, however, during frequency changes in the power supply will lead to a not insignificant falsification in the amplitude of the measuring voltage passing the phase shifting element as well as to a phase displacement deviating from 90.degree., since these phase shifting elements evidence a frequency-dependent attenuation as well as also a frequency-dependent phase shifting. Thereby, during frequency changes in the alternating-current voltage power supply there appears an increased, frequency-dependent measuring error.
For example, from W. Baiers, published "Elektronik Lexikon", 1974, Franckh'sche Verlagsverhandlung, Stuttgart, page 20, there is known the existence of an all-pass transducer. Such an all-pass transducer represents an electrical quadripole whose attenuation characteristic is frequency-independent within wide ranges, which means that frequency changes will not cause amplitude errors, in which the occasioned phase shift is always frequency-dependent.